Method of and apparatus for controlling combustion



Nov. 17, 1925 -1 ,562,0s7

I J. w. GRISWOLD METHOD OF AND APPARATUS FOR CONTROLLING COMBUSTIONFiled Feb, '12, 1920 Patented Nov. 17, 1925.

UNITED STATES JOHN WILLIAM GRISWOLD, OF WARREN,

1,562,087 ENT OFFICE.

PENNSYLVANIA, ASSIGNOR TO HENRY I4.

PAT

YORK, N. Y.

DOHERTY & COMPANY, A COPARTNERSHIP COMPOSED OF HENRY L. DOHERTY I ANDFRANK W. FRUEAUFF, OF NEW METHOD OF AND APPARATUS FOR CONTROLLINGCOMBUSTION. I

Application filed February- To all whom it may concern:

Be it known that I, J OHN WVILLIAM GiuswoLn, a citizen of the UnitedStates of America, residing at Warren, in the county of \Varren, Stateof Pennsylvania, have invented certain new and useful Improvements inMethods of and Apparatus.forCYmtrolling Combustion; and I do" herebydeclare the following tojbe .a'ful'lfclear, and exact descriptien o 1elnven ion, lTus'Wil'heIk' able others skilled in the art to whiEh it ap-JJ JlQjLliQ-TSEO make and use the same.

i the oxygen necessaryf'for burning all of the\ This invention relatesto a method of and an apparatus for controlling the combustion of fuelin a furnace, and more particu larly to a method and apparatus forcontrolling the combustion of-fuel in accordance with the composition ofthe flue gases leaving the furnace. To obtain perfect combustion offuel, it is essential that sufficient air or other source of oxygen besupplied to a furnace to provide fuel. In utilizing the heat ofcombustion of fuel in a commercial furnace, it is very desirable thatall of the products tion shallbe burned before passgg outof' contactwith a heat transferring surffie and \ghihat unburned combustible gasesshall not 10 carried out of the furnace with the exu might insure acomplete 0 haust product though the use of a large excess of air forcombusmgz in a furnace o bustion of the fuel, such an excess is notdesirablebecause it tends to cool the flame temperature and thecombustion zones and acts to carry a large quantity of unabsorbed heatout of the furnace with the e xhaus t products. The 1deal onditions forcombustion, accordingly,

may beobtained when the minimum of air necessary to effect completecombustion of the fuel is supplied to t-hefilrnace. In the practicaloperation of a furnac however. in order to insure that there shall be anadequate supply of air, it is advisab' to provide a slight excess of airover tha necessary for complete combustion, as indlcated by theexistence in the flue gases of a small percentage only of free oxygen. V

The presence of free oxygen or uncons'umed combustible gases in theproducts of combustion may, in certain cases, be indirectly detected bya determination of the amount of carbon dioxide in the flue gases and a\tion of the flue g. ses.

12, 1920. Serial] No. 358,018.

knowledge of the empirical relation between the percentage of carbondioxide and the quantity of unconsumed combustion gases. For instance,in the combustion of a fuel which is with the carbon to form carbondioxide and practically pure carbon, nearly /o, of th oxyg n of'the airwould combine 6 the percentage of carbon dioxide in the flue portion ofcarbon and hydrogen is used the A rough con regulation of combfitiomwvigcentage of carbon dioxide in the flue gas ul accordingly be renderedunreliable. The primary object of the present invention is to provide aprocess of regulating the; combustion of fuel in a furnace in which thevide an apparatus fol; regulating the oo1nbustion of fuel in a furnacebytwhich the supply to said furnace of air for supporting combustion iscontrolled directly by the of combussupply of air to said furnace iscontrolled so quantity of free oxygeninthe products of .7 r

combustion from said furnace.

A further "object of the invention is to i provide a method OfreguIatingthe combustion of fuel-in a boiler furnace, in which the r rate ofcombustion of the fuel is controlled by the boiler pressure, and thecharacter c; E

combustion is controlled by the amount of free oxygen or combustiblegases in the products of combustion in the furnace.

A further object of the invention is to plgvide an apparatusin whichthesupply of air forsupporting combustion is con-.1. tinuouslv under thecontrol of the composi- 1 With these and o ratus described in thefollowing specification and defined in the claims.

then-objects in view, the invention consists in the process and .appa- HThe various features of the invention-are unconsumed oxygen in theproducts of combustion leaving the furnace. To this end, a primarydraftof air is admitted beneath and forced upwardlythroughthe fuel bedwastes":

electric circuit is arrangedto control a draft regulating damper todecrease the supply of secondary air to the furnace when the quantity oftree oxygen in the flue gases rises above a maximum amount.

If liquid or gaseous fuel is used, the supply of fuel, and accordinglytherate of combustion, may be controlled directly by the steam pressureof the boiler. and the entire quantity of air supplied to the furnace,and accordingly the character of rgmbustion, may be controlled by theoxygen content of thefuel gases.

A combustion regulator applied to an ordinary coal fired steam boiler.is shonlg in arid the rate ofcombustion is regulatedby l ig l. In thisarrangement, air for support- M,

increasing or decreasing the draft. To, insure tlfiwmpleteutilization ofthis primary ing ombustig is forced through an air spgp ly pipelOauthegters a furnace 12 un- W of air, a comparat'rveljwthiclrbed o't dera'tuel" grate '14fiLl quantit-y. pi i fuel 1 w which acts similarly to agas.;lla,sgi ng through the p e-wTethegpace un 5 producer to tornLcarbonmonoxide in the upwardly pass ing gases. The priinary-air as it leavesthe tuel bed, therefore, carries with it a considerable amount ofunburned combustible gases. To complete the coml tion of the unburnedgases, a sec ary supply of air slightly in exc of that sufiicient toinsure com 1 combustion is introduce 1e combustiop c haniber above'Wfuel bed.

'lhe quantity 'oi' secondary air supplied to the furhace' is controlleddirectly by the 5 thrgggh a second gas meter. If there is no sp,eedflanthe meter through I passes to the absorption chain er. The two (,0 d toa differential sample of flue gas flows through an absorpjifierentspeeds due to absorption of through a lever 24 denihe grate 14controls the rate offlin amp ed by the steam pressure of the a pressurediaphragm 18 which communicates through a connecting conduit LO ii it Ta steam drum 22 of the boiler. The movement of the diaphragm 18 withvariations in -steam pressure of the boiler is transmitted and aconnecting rod 26 quantity of free oxygen in the products oft,o,the./dainper 16? Asthe pressurein"the combustion passing from thefurnacer Td steam drum 22 of the boiler increases, the

this end a small portion of the products of combustion 1S continuouslywithdrawn from the furnace finefthrougl-iei'gas meteifivhfidiring\rod 26to mov "*Which is filled with an oxygen absorbing substance tocompletely remove any free oxygen contained 111 the products ofcombustion, and from the absorbing chamber passes free gxygenin' theproducts of con'ibiistion, there will be no change in the volume of gaspassing through the absorption chamberand the twoineters placed atopposite sides of saidgabs'orption chamber will be rotated atsubstantially the samelrate of speed. When the flue gas contains freeoxygen, the volume of the gas passing through the absorptionchainber'willbe decreased by the absorption of the oxygen gndothesecond gas tion is withdrawn meter will be mtatedilt a slower rate'o' egas speed of rotation of the gas meters is'equal,

but which is refitted to close an electric draft regulating circuit whenthe meters rotate at free oxygen in the absorption chamber. The

diaphragm movement through the lever 24 and connectmperddtowardclosed'p'b'sitibn Conversely. when the steam pressure in the drum 22falls, the diaphragm 18 is depressed and transmits its 18 rises and thedamper 16 is iWL (spar position.

The combustlon ot tlfe'unburned combustible gases leaying the fuel bedis completed by mean'sdf a secondary airsupply introduced by a branchpipe 28 leading from the pipe 10 to a combustion chamber- EEO above thegrate 14; From the cgnib'ustioiflamber 30 'the products ot/cgmbustfdnpass back and forth in contact with' a bank of Water tubes 32 and leavethe furnace through a flue 34:. a

In testing the products of combustion p g r ugh the flue 34Yfor freeoxygen, 1 Small P rtion of the products of combusfrom the flue 34through b11108 36 and passed through a wet gas meter 38 to determine therate at which the gas is witlidrawn. From the gas meter 38, the

which is-filled with phosphorous or other material capable ofselectively absorbing free oxygen without affecting the otherconstituents of the flue gas. An alkaline solution of pyrogallol may beused, butin that case it will be necessary to tion chamber 40 er 16, theposition of wliih intermittent energizing of the solenoid 88, the switch124 is closed for definite intervals and a lifting force exerted onthe-rod 134 through the energizing of the solenoid 130. In this manner aseries'of lifting impulses is exerted on the lever 138 to close thedamper 116. If this closing action does not suffice to bring the freeoxygen content of the flue gases back to the desired maxi-. mum limit,the contact 50 will continue to move downwardly and to connect the plate68 successively with the branch circuits 80, 82'and '84 and to therebylengthen the periods of time during which current is sent through thesolenoid 88. The effect of increasing the length of time during whichthe solenoid 88 is energized is to increase the length of time duringwhich the switch 124 is closed and the current is sent through thesolenoid 130. In this manner, a more prolonged lifting action is exertedon the rod 134 until the damper 116 is closed sufficiently to bring theoxygen content of the gases in the flue 34 below the desired maxi- .mumlimit. When this point is reached, the

volume ofthe sample of flue gases is substantially undiminished inpassing through the absorption chamber 40 and the meter shaft 48 isrotated at a slightly greater rate of speed than the shaft 46 and thecontact 50 is thereby lifted into its uppermost po: sition. I

When the contact 50 is in its uppermost position, the switch 124 iscontinually held open by the spring 126 and the circuit through thesolenoid 130 is continually open. The weight of the damper operatinglever mechanism acts on the link 118 to slowly open the damper 116 untilthe oxygen content of the ases in the flue 34 rises to the point atwhich the contact 50 is operated in the manner described above. Theaction of the dash pot 142 and the .iston 140- retards the movement ofthe amper operating mechanism to such an extent that a slightchange inthe position of the damper 116 will affect the draft regulating devicebefore the damper 116 will have moved into extreme positions.

While. the invention has been described as applied to a steam boiler inconnection with a device by which the rate of combustion isindependently regulated, the apparatus described above may be used inother --cases without an independent device for regulating the rate ofcombustion. For example, in brass melting and similar metallurgicalfurnaces, the rate of combustion is regulated by hand and combustion iscontrolled to give a maximum temperature. For this purpose, the supplyof air must be so regulated that there will be very little if any excessof air supplied and accordingly little or no free oxygen in the prodnetsof combustion, since the addition of air manner that the amount of freeoxygen in the combustion-products is reduced to the minimum amountnecessary toinsure complete combustion of the fuel. y

The method and apparatus of this invention are similar in certain oftheir broader aspects to the method and apparatus for controlling thecombustion of fuel in a furnace, disclosed in my co-pending application,Serial No. 358,016, filed Feb. 12, 1920. The subject matter common tothis application and application, Serial No. 358,016 is claimed in thelatter application.

Having described the invention, what is claimed as new is:

1.A combustion regulator for furnaces,

comprising means continuously acting to increase the draft-to a furnace,means governed by an electric current for intermittent- 1ydecreasingsaid draft, a gas absorption chamber, means for drawing aportion of the products of combustion from said furnace through the gasabsorption chamber, and means governed by thedecrease in volume of thegas in passing through said absorption chamber for controlling saidelectric current. a

2. A combustion regulator for furnaces, comprising means continuouslyacting to increase the draft to a furnace, means gov-. erned by anelectric current for intermittently decreasing said draft, means forretard ing the speed of said draft increasing and decreasing means, agas absorption chamber, means for drawing a portion of the prodnets ofcombustion from said furnace through the gas absorption chamber, and

means governed byv the decrease in volume of the gases in passingthrough said absorption chamber for controlling said electric current.3. A combustion regulator for furnaces, comprising adamper forcontrolling the draft to a furnace, a lever mechanism acted upon bygravity to move said damper into open position, an electromagnetic meansacting on said lever mechanism to close said damper upon passage ofcurrent thru said electromagnetic means, a. gas absorption chamber,means for-drawing a portion of the products of combustion. from saidfurnace thru the gas absorption chamber,and means governed by thedecrease in volume of the gas in; passing through said absorptionchamber for opening and closing said electric current through saidelectromagnetic damper operating mechanism. p

4. combustion regulator for furnaces,

comprising a damper for controlling the draft to a furnace, a levermechanism acted upon by'gravity to move said damper into open position,an electroi'nagnetic means acting on said lever mechanism to close saiddamper upon passage of current thru said electromagnetic means, a dashpot device acting on said lever mechanism to retard the movement of saiddamper, a gas absorption chamber, means for drawing a portion of theproducts of combustion from said furnace through the gas absorptionchamber, and means governed by the decrease in volume ,of the gas inpassingthrougli said absorption chamber for opening and closing saidelectric current through said electromagnetic damper operatingmechanism.

A combustion regulator for furnaces, comprising means for controllingthe supply of air for supporting combustion to said furnace, a gasmeasuring means, an absorption chamber, a second gas. measuring means,means for drawing a portion of the products of combustion from saidfurnace thru'said first measuring means, said absorption chamber andsecond measuring, means, and means controlled by said gas measuringmeans for operating the means for controlling the air supply to thefurnace.

6. A combustion regulator for furnaces, which comprises meanscontinuously acting to increase the draft to a furnace, means acted uponby the passageof an electric current to decrease said draft. means fordirecting said current thru one of a series of parallel branch electriccircuits, a make and break device arranged. to intermittently open andclose said branch electric circuits for varying lengths of time, andmeans governed by the amount of free oxygen in the products ofcon'ibustion passing from said furnace for connecting said currentthrough the branch electric circuit having the longest period of closingthe oxygen contained in the said products of eon'ibustionincreases.

7. A combustion regulator for furnaces, comprising a gas meter, a gasabsorption chamber, a second gas meter, means for drawing a portion ofthe gas passing from said furnace "successively through said first gasmeter, said absorption" chamber and said second gas meter, adifferential gear driven in opposite directions by the differ.

ences in speed of rotation of said meters, a contact moved by saiddifierential gear, a

series of'parallel branch electric circuits po- 1 sitioned to beseparately and singly closed by said contact, means-for intermittentlyopening said separatebranch circuits for different lengths of time, amagnetic switch connecting the said branch circuits, 2. second circuitclosed by said magnetic switch, a solenoid in said-second circuit and adraft controlling damper operated by said solenoid.

8. A combustion regulator for furnaces, com 'n'ising a gas meter, a gasabsorption cl'iamber, a second gas meter, means for drawing a portion ofthe gas from said furnace successively through said" first gas anelectric circuit for different intervals of time and increasing the timeof each closure as the difference in flow of gas through said metersincreases, a solenoid excited by said current in said circuit, a draftcontrolling damper urged toward open position by a constantly actingforce and toward closed position by said solenoid, and means forretarding the motion of said damper.

10. A combustion regulator for furnaces, coi'nprising a gas meter, atgas absorption chamber, a secondgas meter, means for drawing a portionof the gas passing through said furnace successively through said firstgas meter. said absorption chamber and said second gas meter, a seriesof parallel branch electric circuits, a contact operated by thedifference in volume of gas passing through said meters to separatelyand singly close said branch electric circuits, means-for intermittentlyopening and closing said branch electric circuits for different lengthsof time, a magnetic switch arranged to be closed during the passage ofintermittent currents through. said branch electric circuits, and meanscontrolled by said second circuit for operating the draft cont-rollingdamper'of said furnace.

11. A combustion regulator for furnaces, comprising means constantlyacting to increase the draft to a furnace, means for constantly testingthe quantity of free oxygen in the products of combustion from saidfurnace, and means acting intermittently for increasingly longer periodsof time, as the quantity of free oxygen'increases beyond a certainpercentage, to decrease said draft. a I

12. The method of regulating combustion in furances, which comprisescontinuously removing a sample of the flue gases from a furnace,continuously testing sald sam' ple of flue gases for free oxygen,continu- 1 is below a certain percentage, and decreasintermittentenergizing of the solenoid 88, the switch 124 is closed for definiteintervals and a lifting force exerted on the rod 134 through theenergizing of the solenoid 130. In this manner a seriesof liftingimpulses is exerted on the lever 138 to close the damper 116. If thisclosing action does not suffice to bring the free oxygen content of theflue gases back to the desired maxi: mum limit, the contact 50 willcontinue to move downwardly and to connect the plate 68 successivelywith the branch circuits 80, 82'and 84 and to thereby lengthen theperiods of time during which current is sent through the solenoid 88.The effect of increasing the length of time during which the solenoid 88is energized is to increase the length of time during which the switch124 is closed and the current is sent through the solenoid 130. In thismanner, a more prolonged lifting action is exertedon the rod 134 untilthe damper 116 is closed sufliciently to bring the oxygen content of thegases in the flue 34 below the desired maximum limit. When this point isreached, the volume ofthe sample of flue gases is substantiallyundiminished in passing through the absorption chamber 40 and the metershaft 48 is rotated at a slightly greater rate fore the damp with adevice by which of speed than the shaft 46 and'the contact 50 is therebylifted into its uppermost position.

When the contact 50 is in its uppermost position, the switch 124 iscontinually held open by the spring 126 and the circuit through thesolenoid 130 is continually open. The weight of the damper operatinglever mechanism acts on the link 118 to slowly open the damper 116 untilthe oxygen content of the gases in the flue 34 risesto the point atwhich the contact 50 is operated in the manner described above. Theaction of the dash pot 142 and the iston 140 retards the movement of theamper operating mechanism to such an extent that a slight change in theposition of the damper 116 will affect the draft regulating device beer116 will have moved into extreme positions.

While the invention has been, described as applied to a steam boiler inconnection the rate of combustion is independently regulated, theapparatus described above may be used in other cases without anindependent device for regulating the rate of combustion. For example,in brass melting and similar metallurgical furnaces, the rate ofcombustion 1s regulated by hand and combustion is controlled to give amaximum temperature. For this purpose, the supply of air must be soregulated that there will be very little if any excess of air suppliedand accordingly little or no free oxygen in the prod since the addltlonof air nets of combustion,

above that necessary for complete combustion reduces the temperatureobtained because of the cooling action of the excess air. In this case,therefore, the above described combustion control device is used,without an automatic device for controlling the rate of combustion, tocontrol the total amount of air supplied to the furnace in such a mannerthat the amount of free oxygen in the combustion products is reduced tothe minimum amount necessary to insure complete combustion of the fuel.

The method and apparatus of this invention are similar in certain oftheir broader aspects to the method and apparatus for controlling thecombustion of fuel in a furnace, disclosed in my co-pending application,Serial No. 358,016, filed Feb. 12, 1920. The subject matter common tothis application and application, Serial No. 358,016 is claimed in thelatter application.

Having described the invention, what is I crease the draft to a furnace,means governed by an electric current for intermittentlydecreasing saiddraft, means for retard ing the speed of said draft increasing anddecreasing means, a gas absorption chamber, means for drawing a portionof the products of combustion from said furnace through the gasabsorption chamber, and means governed by the decrease in volume of thegases inpassing through said absorption chamber for controlling saidelectric current.

3. A combustion regulator for furnaces, comprising a damper forcontrolling the draft to a furnace, a lever mechanism acted upon bygravity to move said damper into open position, an. electromagneticmeans acting on said lever mechanism to close said comprising a damperfor controlling the draft to a furnace, a lever mechanism acted uponby'gravity to move said damper into open position, an electron'iagneticmeans acting on said lever mechanism to close said damper upon passageof current thru said electromagnetic means, a dash pot device acting onsaid lever mechanism to retard the movement of said damper, a gasabsorption chamber, means for drawing a portion of the products ofcombustion from said furnace through the gas absorption chamber, andmeans governed by the decrease in volume of.the gas in passing throughsaid absorption chamber for opening and closing said electric currentthrough said electromagnetic damper operating mechanism.

A. combustion regulator for furnaces, comprising means for controllingthe supply of air for supporting combustion to said furnace, a gasmeasuring means, an absorption chamber, a second gas measuring means,means for drawing a portion of the products of combustion from saidfurnace thru said first gas measuring means, said absorption chamber andsecond measuring. means, and means controlled by said gas measuringmeans for operating the means for controlling theair supply to thefurnace.

6. A combustion regulator for furnaces, which comprises meanscontinuously acting to increase the draft to a furnace, means acted uponby the passage-of an electric current to decrease said draft. means fordirecting said current thru one of a series of parallel branch electriccircuits, a make and break device arrangedv to intermittently open andclose said branch electric circuits for varying lengths of time, andmeans governed by the amount of free oxygen in the products ofcombustion passing from said furnace for connecting said current throughthe branch electric circuit having the longest period of closing as theoxygen contained in the said products of combustion increases.

7 A-combustion regulator for furnaces, comprising a gasmeter, a gasabsorption chamber, a second gas meter, means for drawing a portion ofthe gas passing from said furnace successively through said first gasmeter, said absorption" chamber and said second gas meter, adifferential gear driven in opposite directions by the differ-.

ences in speed of rotation of said meters, a contact moved by saiddifferential gear, a

series of parallel branch'electriccircuits po- 1 sitioned to beseparately and singly closed by said contact, means-for intermittentlyopening said separatebranch circuits for different lengths of time, amagnetic switch connecting the said branch circuits, a second circuitclosed by said magnetic switch, a solenoid in saidsecond circuit and adraft controlling damper operated by said solenoid.

8. A combustion regulator for furnaces, comprising a gas meter, a gasabsorption chamber, a second gas meter, means for drawing a portion ofthe gas from said furnace successively through said first gas meter,said absorption chamber and second gas meter, and means controlled bythe dif fcrence in speed of rotation of said meters for controlling thedraft to said furnace.

9. A combustion regulator for a furnace, comprising means for measuringthe rate of {low of gas, an absorption chamber,'a sec' ond means formeasuring the rate of flow of gas, means for drawing a portion of theproducts of combustion from said furnace successively through said firstmeasuring means, said absorption chamber and said second measuringmeans, means controlled by said gas measuring .means for closing anelectric circuit for different intervals of time and increasing the timeof each closure as the difference in flow of gas through said metersincreases, a solenoid excited by said current in said circuit, a draftcontrolling damper urged toward open position by a constantly actingforce and toward closed position by said solenoid, and means forretarding the motion of said damper.

,10. A combustion regulator for furnaces, comprising a gas meter, a gasabsorption chamber, a secondgas meter, means for drawing a portion ofthe gas passing through said furnace successively through said first gasmeter. said absorption chamher and said second gas meter, a series ofparallel branch electric-circuits, a contact operated by the differencein volume of gas passing through said meters to separately and singlyclose said branch electric circuits, means for intermittently openingand clos ing said branch electric circuits for different lengths oftime, a magnetic switch arranged to be closed during the passage ofintermittent currentsthrough said branch electric circuits, and meanscontrolled by said second circuit for operating the draft cont-rollingdamper of said furnace.

11. A combustion regulator for furnaces, comprising means constantlyacting to increase the draft to a furnace, means for constantly testingthe quantity of free oxygen in the products of combustion from saidfurnace, and means acting intermittently for increasingly longer periodsof time, as the quantity of free oxygen'increases beyond a certainpercentage, to de- 1 crease said draft.

12. The method, of regulating combustionin furances, whlch comprisescontlnuously removing a sample of the flue gases from when the contentof oxygen in the flue gases is below a certain percentage, anddecreasing the draft when the quantity of free oxygen increasesabovesaid fixed percenta e.

13. The method of regulating combustion in furnaces whlch comprisescontinuously removing a sample of the flue gases from a furnace,continuously testing said sample of flue gases for free oxygen,continuously increasing the draft to the furnace when the content ofoxygen in the flue gases is below a certain percentage, andintermittently decreasing the draft when the percentage of oxygenincreases beyond a fixed q naces which comprises means governed by thesteam pressure in said boiler for controlling the rate of combustion insaid furnace, an air supply for completing the combustion of fuel insaid furnace, means continuously acting to increase said air supply tosaid furnace, means governed by an electrio, current-for intermittentlydecreasing said draft, a gas absorption chamber, means for drawing aportion of the products of combustion from said furnace through said gasabsorption chamber, and means governed by the decrease in volume of gasin passing through said absorption chamber for controlling said electriccurrent. 16. A combustion regulator for boiler furnaces which comprisesmeans governed by the steam pressure in said boiler for controlling therate of combustion in said furnace, an air supply for completingcombus-f tion in said furnace, a gas meter an ab'sorption chamber, asecond gas meter, means for drawing a portion of the products ofcombustion successively through said first gas meter, said absorptionchamber and said sec ond gas meter andmeans governed by the differencein speed of rotation of said meters for controlling said air supply tosaid furnace.

17. A combustion regulator for furnaces c'om rising a primary air supplyfor control mg the rate of combustionof fuel in said furnace, meansigoverned by the steam pressure .in said boi er fox-controlling the rateof suppl of said primary air, a second air supply or completingcombustion of fuel in said furnace, a gas meter, an absorpgases risesbeyond a fixed pertion chamber, a second gas meter, means for drawing-aportion of tie products of combustion successively through said firstmeter, said absorption chamber and said second meter and means governedby the difference in the speed of rotation of said metersfor controllingthe supply of secondary air to said furnace.

18. In a furnace having primary and secondary air supplies, a combustionregi'ilator for furnaces comprising an absorption cham-. ber, means forpassing a portion of the flue gases from the furnace continuouslythrough the absorption chamber, andmeans for au-' tomaticallycontrolling the supply. of secondary air to the furnace in accordancewiththe amount of gas absorbed in said chamber.

.19. A combustion regulator for furnaces comprising an absorptionchamber adapted to absorb oxygen only from the furnace gases, means forpassing a portion of the gases from said furnace through the absorptionchamber, and means for controlling the supply of air to the furnace inaccordance with the extent-to which the volume of the furnace gases isreduced by-the' absorption of oxygen from them.

20. A'combustion regulator for furnaces comprising means for removingthe free oxygen from a portion of the flue gases and means'forcontrolling :the' six pl of air to the furnace in accordance with t eratio of the volume of gasesiibefore' and after the removalof theoxygen.

21. Th in-furnaces which comprises continuously removing a sample streamof the flue gases e method of regulating combustion from a furnace,effecting a continuous analy-- sis of the chemical composition of saidsample, metering the volume ofthegasesbefore and after the analysis andautomatically governing the draft on said furnace in ac-,

cordance with the volume change of the sam ple effected by the analysis.

' 22, The method of regulating comfbustion' in furnaces which comprisescontinuously removing asample stream of flue gases from a furnace,efiectmg-awontinuous chemical combination of the free oxygen in saidsample, measuring the volume change in said sample produced by saidcombination and regulating the amount of draft'on the furnaceinaccordance with said volume change.

23 ."The methodof regulating combustion in furnaces which comprisescontinuously removing a sample stream of the flue gases from a furnace,continuously absorbing the free oxygen content of said'sample' and relating the draft to the furnace by a mec anism responsive to the volumechange in said sample before and after the absorption. In testmronwhereof I aflix m signature. J OHN WILLIAM GRI WULD.

